This invention relates to a machine for forming a cable harness which is a bundle of various wires for use in providing electric connections among a plurality of subunits in a telephone exchanger, a like exchanger, an electronic computer, or a similar electric or electronic device. The subunits may be printed circuits.
A conventional automatic cable harness forming machine comprises a harness laying head and a numerical control unit for driving the head in accordance with a desired pattern for each wire of the cable harness. The machine is used in combination with a harness board on which the cable harness is to be formed. However, a conventional machine still has many defects which must be obviated before field use of such machines is rendered feasible. Typical defects reside in means for enabling the head to dispose of the wires from which the wire segments forming the cable harness are subsequently cut, in means for processing a wire end, and in means for holding the wires at their bends in the general pattern.
In one type of the conventional machines, a plurality of reels for the wires are carried by the head. It is possible with this type to simplify the mechanism for supplying predetermined one of the wires to the head. The head, however, can accommodate only several kinds of wires, whereas a cable harness for a crossbar telephone exchanger comprises wire segments formed of wires of about twenty kinds. In addition, it has been difficult to achieve controlled tension in the wire being laid on the harness board.
In another type of the conventional machines, such as disclosed in Japanese Pat. Disclosure No. Syo 48-59398, the head lays the wire in an endless manner on the harness board for the wire segments of one and the same wire. The wire is subsequently manually cut into the wire segments. This is troublesome, results in loss of the wires, and is liable to erroneous cutting. These disadvantages grow more serious in a cable harness comprising as many as two thousand wire segments for use in a crossbar exchanger of medium size. In an attempt for obviating the disadvantages, the head is equipped with a cutter for cutting the wire into a wire segment as soon as the head laid each of the wire on the harness board. It, however, is difficult even with this attempt to control the skinner length which is a length between a wire end tip and the point from where the wire end branches.
A harness board has a plurality of pins attached thereto in conformity with the pattern of the cable harness to be formed thereon. The pin positions may be changeable. The pins retain the wire ends and hold or guide the bends of the wire segments. The pins, however, are unreliable, require a wide area around each thereof to retain and hold the wire segments, and are accordingly unsuited for a cable harness having closely spaced branches, or wire segment groups, and twigs, or wire segment subgroups each comprising ten to twenty wire segments, such as one for the crossbar switchboard use where the distances between the adjacent branches and between the adjacent twigs are about 50 mm and only 6.5 mm, respectively.